Radio broadcasting system and method providing continuity of service

Abstract

A system and method to provide continuity of service in a radio broadcasting system, wherein the radio broadcasting system includes at least one modem using the COFDM technique, and transmits N time-frequency cells modulated independently of one another. A number N 1 of cells conveying digital audio signal S 1 and a number N 2 of cells conveying analog audio signal S 2 are transmitted to a receiver. When the receiver cannot decode the signal in the N 1 cells, the receiver replaces the digitized audio signal S 1 with the analog signal S 2 .

1. A method to provide continuity of service in a radio broadcasting system, wherein the radio broadcast system includes at least one modem using a COFDM technique, and said radio broadcasting system is configured to transmit N time frequency cells modulated independently of one another, the method comprising:
 at transmission,
 sending a number N 1  of cells conveying signals for transmission of a digitized audio signal S 1 , and 
 sending a number N 2  of cells conveying signals for transmission of an analog signal S 2 ; 
 
 at reception,
 differentiating, in a received signal Sr, between at least the digitized audio signal S 1  and the analog signal S 2 ; 
 
 replacing the digitized audio signal S 1  by the analog signal S 2  conveyed by the cells N 2  when the signals of the N 1  cells cannot be decoded, 
 wherein a proportion of cells N 1  for a passband of about 10 kHz ranges from 50% to 80% of a quantity N of available cells. 
 
   
   
     2. A method to provide continuity of service in a radio broadcasting system, wherein the radio broadcast system includes at least one modem using a COFDM technique, and said radio broadcasting system is configured to transmit N time frequency cells modulated independently of one another, the method comprising:
 at transmission,
 sending a number N 1  of cells conveying signals for transmission of a digitized audio signal S 1 , and 
 sending a number N 2  of cells conveying signals for transmission of an analog signal S 2 ; 
 
 at reception,
 replacing the digitized audio signal S 1  by the analog signal S 2  conveyed by the cells N 2 , when the signals of the N 1  cells cannot be decoded, wherein 
 
 at transmission, one or more preprocessing steps are performed, including introducing a delay for the analog signal S 2 . 
 
   
   
     3. The method according to  claim 2 , further comprising compressing the dynamic range before introducing the delay for the analog signal S 2 . 
   
   
     4. The method according to  claim 2 , further comprising:
 at reception, separating at least the digitized audio signal S 1  from the signal analog S 2 ; and 
 performing validation of the digitized audio signal S 1  in decodable or non-decodable form before the replacing step. 
 
   
   
     5. The method according to  claim 2 , further comprising:
 at reception, post-processing the analog signal S 2 , wherein said post-processing includes at least rejecting background noise. 
 
   
   
     6. The method as in any one of  claims 2  to  5 , wherein a proportion of cells N 1  for a passband of about 10 kHz ranges from 50% to 80% of a quantity N of available cells. 
   
   
     7. A radio broadcasting system including at least one modem using a COFDM technique, said modem being represented in a time frequency space by several elementary cells comprising N available cells, wherein the system comprises:
 a transmitter, wherein said transmitter includes,
 a device configured to distribute signals for transmission of a digitized audio signal S 1  in a number N 1  of cells and signals for the transmission of analog audio signals S 2  in a number N 2  of cells; and 
 a device configured to obtain a compression of a dynamic range of the analog audio signal S 2 , 
 
 a receiver, wherein said receiver includes,
 a device configured to differentiate, in a received signal Sr, between at least the digitized audio signal S 1  and the analog audio signal S 2 , 
 a device configured to determine if the digitized audio signal S 1  is in decodable form, and 
 a device configured to replace the digitized audio signal S 1 , which is not in decodable form, with the analog audio signal S 2 . 
 
 
   
   
     8. A radio broadcasting system comprising including at least one modem using a COFDM technique, said modem being represented in a time frequency space by several elementary cells comprising N available cells, at least one transmitter and at least one receiver, wherein the system comprises at least one of the following elements:
 a transmitter, wherein said transmitter includes,
 a device configured to distribute signals for transmission of a digitized audio signal S 1  in a number N 1  of cells and signals for the transmission of analog audio signals S 2  in a number N 2  of cells and 
 a device configured to introduce a delay into the analog audio signal S 2 , said transmitter further includes at least one of, 
 a lowpass filter at the receiver configured to filter the analog audio signal S 2 , 
 a system configured to sample the analog audio signal S 2 , and 
 a device configured to obtain a compression of a dynamic range of the analog audio signal S 2 ; 
 
 a receiver, wherein said receiver includes,
 a device configured to differentiate, in a received signal Sr, between at least the digitized audio signal S 1  and the analog audio signal S 2 , 
 a device configured to determine that the digitized audio signal S 1  is in decodable form, and 
 
 a device configured to replace the digitized audio signal S 1 , which is not in decodable form, with the analog audio signal S 2 . 
 
   
   
     9. A radio broadcasting system comprising including at least one modem using a COFDM technique, said modem being represented in a time frequency space by several elementary cells comprising N available cells, at least one transmitter and at least one receiver, wherein the system comprises at least one of the following elements:
 a transmitter, wherein said transmitter includes,
 a device configured to distribute signals for transmission of a digitized audio signal S 1  in a number N 1  of cells and signals for the transmission of analog audio signals S 2  in a number N 2  of cells; 
 
 a receiver, wherein said receiver includes,
 a device configured to differentiate, in a received signal Sr, between at least the digitized audio signal S 1  and the analog audio signal S 2 , 
 a device configured to perform a windowing on the received signal Sr on a portion of the received signal that is supposed to be stable, 
 a device configured to determine if the digitized audio signal S 1  is in decodable form, 
 a device configured to replace the digitized audio signal S 1 , which is not in decodable form, with the analog audio signal S 2 , and 
 a device configured to perform processing operations on the analog audio signal S 2 , wherein said processing operations include at least rejecting background noise. 
 
 
   
   
     10. The system according to any one of  claims 7  to  9 , wherein a number of cells N 1  ranges from 50% to 80% of the value of a number of free cells N in the modem for a frequency band of about 10 KHz. 
   
   
     11. The method according to  claim 2 , wherein the preprocessing steps further include lowpass filtering and sampling.